1. Field of the Invention
The present invention relates to a resonator including an inductor and a capacitor and to a band pass filter including this resonator.
2. Description of the Related Art
Hitherto, as a band pass filter including a plurality of resonators, the band pass filter disclosed in International Publication No. 2009/41294 is known. An example of this filter is shown in FIG. 9. In this filter, a capacitor is formed by a ground electrode 109 disposed on a dielectric layer 101 and capacitor electrodes 111 through 113 disposed on a dielectric layer 102. A plurality of inductor electrodes are formed by via-electrodes 131 through 136 and line electrodes 116 through 118. Loop surfaces of these inductor electrodes overlap each other, as viewed in a stacking direction of the dielectric layers. These inductor electrodes and the capacitors form LC parallel resonators. The line electrode 117 which overlaps the line electrodes 116 and 118 is formed in a meander line shape.
By forming the line electrode 117 in a meander line shape, the line length of the line electrode 117 can be relatively increased within a limited exclusive area, so that the inductance can be set to be a desired value. However, it has been found that a sufficient Q factor of the resonator is not obtained if the line electrode 117 is formed in a meander line shape. That is, in the line electrode 117 formed in a meander line shape, the concentration of a current in areas indicated by the hatched portions in FIG. 5C is observed, which causes a decrease in the Q factor.